Synthesis of 2D Tin Sulfide [SnS_(x=1,2)] Layers by Proximity Evaporation: Thermodynamic Phase Tuning and Optical Photoresponsivity

Fabricating large-area two-dimensional (2D) metal dichalcogenide layers with stoichiometry and uniformity has been a research focus over the past few years. Most of the time, the types of growth methods determine of quality of the 2D layers, and in turn, they affect their electronic properties and applications. Here, we report a nonconventional facile way of synthesizing nearly single crystalline 2H hexagonal SnS₂ and orthorhombic SnS layers via proximity evaporation, where the distance between the Sn precursor film and the target substrate is ~1 mm. This short distance provides self-limiting 2D layers with good uniformity and stoichiometry. The phase transition study was carried out by varying the growth temperature (300–650°C). Pure phases of SnS₂ and SnS were formed at the optimum temperatures. Large hexagonal SnS₂ sheets with a 1:2 stoichiometric ratio were observed. The high-resolution transmission electron microscopy (HRTEM) and Raman spectra further revealed the 2H phase of SnS₂ sheets. Photoresponse studies of both pure phases of SnS and SnS₂ showed significant photoresponse with improved photocurrent. Our synthesis method can be extended to grow large-area uniform sheets of other 2D materials having lower heat of formation. Graphical Abstract: [Figure not available: see fulltext.]